Metabolic engineering of Escherichia coli for the production of 1-propanol

An engineered Escherichia coli strain that produces 1-propanol under aerobic condition was developed based on an l-threonine-overproducing E. coli strain. First, a feedback resistant ilvA gene encoding threonine dehydratase was introduced and the competing metabolic pathway genes were deleted. Further engineering was performed by overexpressing the cimA gene encoding citramalate synthase and the ackA gene encoding acetate kinase A/propionate kinase II, introducing a modified adhE gene encoding an aerobically functional AdhE, and by deleting the rpoS gene encoding the stationary phase sigma factor. Fed-batch culture of the final engineered strain harboring pBRthrABC-tac-cimA-tac-ackA and pTacDA-tac-adhEmut allowed production of 10.8 g L−1 of 1-propanol with the yield and productivity of 0.107 g g−1 and 0.144 g L−1 h−1, respectively, from 100 g L−1 of glucose, and 10.3 g L−1 of 1-propanol with the yield and productivity of 0.259 g g−1 and 0.083 g L−1 h−1, respectively, from 40 g L−1 glycerol.